zoom not working

[vinocell]

Hello,

I just wrote a simple plugin to have my ImageCanvas embedded into a JFrame
with the ability to zoom from a square ROI.
This is why I created the HiddenImageWindow class with an empty redefined
show() and a setVisible(false) call in the constructor, to make sure this
window is not going to be displayed (while being able to grab its canvas).
After this trick I just copied the zoomToSelection() function in
http://rsb.info.nih.gov/ij/source/ij/plugin/Zoom.java to be able to run it
from a square ROI.
However it doesn't work (especially after a second zoom) and the canvas
turns to grey. Any idea why this code printed below fails ?

Thanks,

Vinocell.



import ij.*;
import ij.process.*;
import ij.gui.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import ij.io.OpenDialog;
import ij.io.Opener;
import ij.plugin.*;
import ij.plugin.PlugIn;

import java.awt.*;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import javax.swing.*;


public class JFrameZoom_ implements PlugIn, MouseListener {
    /** GUI main window */
    protected JFrame _mainWindow;
    /** GUI subpanel */
    protected JPanel _pan;
    /** DICOM, jpeg, tiff, ... phase images. */
    protected ImagePlus _impPhase;
    /** Window phase images. */
    protected ImageWindow _winPhase;
    /** Canvas containing one of the phase images. */
    protected ImageCanvas _canvasPhase;

    public void run(String arg) {
    // Input files
    OpenDialog od = new OpenDialog("Open Image Sequence...", arg);
    String directory = od.getDirectory();
    String fileName = od.getFileName();
    Opener op = new Opener();
    // Create ImagePlus & Canvas & HiddenImageWindow
    _impPhase = op.openImage(directory,fileName);
    _canvasPhase =  new ImageCanvas(_impPhase);
    _winPhase = new HiddenImageWindow(_impPhase,_canvasPhase);
    _canvasPhase.addMouseListener(this);

    _pan = new JPanel();
    _pan.add(_canvasPhase);
     //Display the window.
    _mainWindow = new JFrame("FLUX");
    _mainWindow.add(_pan);
    _mainWindow.pack();
    _mainWindow.setVisible(true);
    }

    /** Implement the interface MouseListener */
    public void mouseReleased(MouseEvent e) {
        if (e.getSource().equals(_canvasPhase) &&
            _impPhase.getRoi()!= null &&
            IJ.shiftKeyDown()) {
            zoomToSelection(_impPhase, _canvasPhase);
            _impPhase.killRoi();
        }
    }

    /** Implement the interface MouseListener */
    public void mousePressed(MouseEvent e) {}

    /** Implement the interface MouseListener */
    public void mouseEntered(MouseEvent e) {}

    /** Implement the interface MouseListener */
    public void mouseExited(MouseEvent e) {}

    /** Implement the interface MouseListener */
    public void mouseClicked(MouseEvent e) {}

    // Copy of the zoom plugin as defined in ImageJ
    void zoomToSelection(ImagePlus imp, ImageCanvas ic) {
        Roi roi = imp.getRoi();
        ic.unzoom();
        if (roi==null) return;
        Rectangle w = imp.getWindow().getBounds();
        Rectangle r = roi.getBounds();
        double mag = ic.getMagnification();
        int marginw = (int)((w.width - mag * imp.getWidth()));
        int marginh = (int)((w.height - mag * imp.getHeight()));
        int x = r.x+r.width/2;
        int y = r.y+r.height/2;
        mag = ic.getHigherZoomLevel(mag);
        while(r.width*mag<w.width - marginw && r.height*mag<w.height -
marginh) {
            ic.zoomIn(ic.screenX(x), ic.screenY(y));
            double cmag = ic.getMagnification();
            if (cmag==32.0) break;
            mag = ic.getHigherZoomLevel(cmag);
            w = imp.getWindow().getBounds();
        }
    }

    /**
     * The class HiddenImageWindow hides the frame that IJ uses to display
the image.
     */
    private class HiddenImageWindow extends ImageWindow {
        /** For the serialization */
        private static final long serialVersionUID = 0L;

    public HiddenImageWindow(ImagePlus imp, ImageCanvas ic) {
        super(imp, ic);
        setVisible(false);
    }

    public void show() {}
    }
}